Should we list him as 26 since that is obviously wrong? It's 2-3 vs 1.
- databook says he is 26 (1)
- databook also says he became Genin at 9 (against 1)
- manga says the academy massacre had happened 10 years prior to Part I. by his yet-to-be-a-ninja-himself hand (against 1)
- obviously, the earliest Obito could control Yagura and create Bloody Mist was about 20 years back at most (maybe against 1)
Well, 29-20/21=8/9, fits within the range for its sake, just barely though. So 26 only could be correct by assuming that Obito was fast enough to become "4th Mizukage" at his 13-14 just after massacring those Mist nin. Possible, but not that probable, more likely Obito took control of Yagura a bit later, rendering Zabuza's age wrong again. Even if not, there's still the incident of academy massacre stated to had taken place 10 years prior to Part I. as his Genin age as 9.